This research investigates the ability of three- and four-month-old human infants to perceive and learn about the unity and the boundaries of certain objects and events. Through observations of exploration and attention, the research first focuses on infants' perception of biomodally specified events: their ability to determine whether concurrent patterns of light and sound specify one unitary event or two separate episodes. These methods are used next to investigate infants' visual perception of partly occluded objects: their ability to determine whether a complete or broken object continues behind a screen that covers its center. Finally, the studies focus on infants understanding of objects that move from view: their ability to determine whether an object persists or is changed by a transformation that takes it from sight. Experiments probe: (1) infants' early developing capacities to perceive the unity and boundaries of objects, (2) their ability to extend these capacities by acquiring knowledge, and (3) the nature of the knowledge that they acquire. These experiments thus explore the constraints that early perceptual and learning abilities place on the human capacity for intersensory functioning, visual object perception, and understanding about object permanence.